Acute respiratory infection (ARI) is responsible for 19% of all deaths worldwide among children less than five years old. Environmental factors such as air pollution have been hypothesized to increase the risk of incidence for ARI in young children. Malnutrition is also known to suppress the immune system that renders a child more susceptible to ARI. This five-year traineeship aims to link environmental pollutants, while controlling for host nutritional factors, to an overall increase in the incidence of respiratory diseases in Ecuadorian children. Air pollution in Quito, Ecuador will be closely monitored by the City of Quito and using mobile handheld monitors to allow a time-series and geographical analysis of respiratory disease in a cohort of children already enrolled in an NIH-funded study. These data will be used to statistically analyze adverse respiratory health outcomes in variably malnourished Ecuadorian children as it relates to air pollution. In addition, molecular and microbiologic analysis will establish a spectrum of pathogens that cause disease.